I have one that you all will love. I have a home that the previous owner had a contractor come in and replace the wood main center beam with a 6" steel I-beam. It looks like the floor was jacked up a couple inches and steel beams put in. So far so good, right? Well, right above the steel beam, the entire span of it, the massive floor timbers were notched approximately 6" wide x 4" deep into each joist. This is a very old home and the floor joists are dimentional 2x10's. So, effectively, whoever notched the beam essentially made them 2x6's right in the center of their span. They then sistered standard 2x8 lumber in order to span the groove, using lag screws on one side of each floor joist apparently trying to repair the notch that was made by the previous "engineer". Apparently this looked acceptable to them. Well, now the floor rests on these sistered pieces of wood that are about 2' long and lagged twice to the original joist, on one side only. Guess what, they are literally twisting and pulling away from the original joists due to the weight.

So, now here comes the question. How in the world does this get fixed? It is a 2 story, 1,300 sq foot house. Would it better to jack up on either side of the beam to the desired height, remove the sistered piece and resister with proper lam beams, then install new columns with proper footings? If so, how long and big should the sistered section be, assuming place on both sides of joist and carriage bolted together. Thanks much!

Ron6519

04-04-2009 06:39 PM

Post some photos of this. It's easier to deal with.
Ron

Bob Mariani

04-05-2009 08:06 AM

Can you install hangers to support the original joists to the beam? Also add blocking to stop the twisting.

AllanJ

04-05-2009 09:35 AM

It is my belief that, generally, notching the joists a little to let a support beam pass perpendicularly underneath does not hurt. But it must not be overdone, for example leave only three inches of height to the joist.

I would use as sistering, four feet of material of the same kind (2x10 here) with the same notch cut out from one end and slipped above the suppport beam. For a center beam use two of them, one on each side of the beam, one on each side of the joist respectively.

You'll need to snip off flooring nails protruding below the subfloor to slide the sister in place.

Perhaps a structural engineer might want to comment on this idea. No sistering. Drill pilot holes in, and glue/nail a square of wood, grain vertical, on the joist next to the support beam and notch. In this case (2x10 joists) it would be about 9-1/2 inches square. Its purpose is to prevent the joist from splitting lengthwise at the notch if the joist would want to bow under the weight of what it is supporting.

How did they use a continuous 2x8 as a sister passing above the beam when the clearance after notching the original joists was about 6 inches?

All this assumes that the support beam is truly a support beam. I would not have expected the jerry rigged sistering to twist and warp unless the steel beam had sagged in which case the steel beam needs footinged column supports along its length and jacking as part of the solution.

With a proper support beam, the notches in the joists are considered end notches, not center span notches.